JP2003261303A - Reforming reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reforming reactor capable of decreasing the temperature gradient of a reforming catalyst. <P>SOLUTION: The reforming reactor provided with reforming catalyst 11, 13, 15 for producing reformed gas by reforming a fuel gas is provided with a 1st fuel gas inlet part 7, a throttle plate 19 for decreasing the flow passage area for the fuel gas in the fuel gas introducing part 9, a stirring part 20 for stirring the fuel gas and a 2nd fuel gas inlet part 8. The 1st fuel gas inlet part 7 is arranged at the end part of a fuel gas introducing part 9 for introducing the fuel gas to the reforming catalyst 11, 13, 15 and the fuel gas is introduced through the 1st fuel gas inlet part 7 to swirl in the fuel gas introducing part 9. In the 2nd fuel gas inlet part 8, the fuel gas is introduced from the side surface of the stirring part 20 to swirl in the opposite direction to the swirling direction of the fuel gas supplied from the 1st fuel gas inlet part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a reforming reactor of a fuel cell system.

[0002]

2. Description of the Related Art As a conventional reforming reactor, Japanese Patent Laid-Open No. 9-
The one disclosed in Japanese Patent No. 306533 is known. This is a reforming reactor in which an outer tubular member is arranged so that the inner tubular member penetrates, and a heat exchanger capable of supplying heat gas to the outer tubular member and passing it to supply heat to the inner tubular member is incorporated. Is. The wall material of the inner cylinder member is hollow, and in the case of methanol reforming, a heat storage material such as LiNO ₂ having a melting point in the reaction temperature range of 200 to 300 ° C. is contained inside the wall material. A sufficient amount of heat is supplied to this heat storage material in advance, and the heat storage material is melted to be in a liquid phase state.

In such a reforming reactor, when it becomes necessary to rapidly increase the amount of reforming fuel gas produced in the reforming reactor, the amount of heat supplied from the heating gas passing through the outer cylinder member is delayed. Even if it occurs, latent heat is dissipated when the heat storage material undergoes a phase transition to a solid phase, so that the amount of heat required for reforming can be sufficiently covered.

[0004]

[Problems to be solved by the invention] However,
In Japanese Patent Laid-Open No. 9-306533, the fuel gas is non-uniformly supplied to the reforming reaction section that converts the fuel gas into the reformed gas by using the heat supplied from the heated gas, or the non-uniformity is caused by the heated gas. There is a problem that a temperature gradient occurs in the reforming reaction section due to the temperature rise. as a result,
In the reforming reactor, a region where the temperature becomes low or high partially occurs.

When steam reforming is carried out using methanol as the raw fuel, the conversion rate is deteriorated in the low temperature region due to the reduction of the reforming efficiency. In addition, when the reforming gas such as H ₂ , CO, and CO ₂ generated by the reforming reaction is exposed to the high temperature region, the reverse shift reaction in which CO is generated from H ₂ and CO ₂ is promoted, so that the reforming is performed. There is a problem that CO in the gas increases and exceeds the allowable range of the fuel cell.

[0006] Therefore, an object of the present invention is to provide a reforming reactor capable of reducing the temperature gradient in the reforming reaction section.

[0007]

[Means for Solving the Problems] The first invention is to introduce a reforming reaction section having a reforming catalyst for producing reformed gas by reforming the fuel gas, and introducing the fuel gas to the reforming reaction section. And a fuel gas introducing section for introducing the fuel gas so as to swirl upstream thereof, and a flow area of the fuel gas in the fuel gas introducing section. And a stirring section that stirs the fuel gas at the narrowest part of the narrowed section.

A second aspect of the present invention is the second aspect of the first aspect, wherein the second fuel gas inlet portion supplies the fuel gas so that the fuel gas is swirled in a direction opposite to the swirling direction of the fuel gas supplied from the first fuel gas inlet portion. Was placed in the stirring section.

According to a third aspect of the invention, water is introduced from the first fuel gas inlet and hydrocarbon fuel is introduced from the second fuel gas inlet.

A fourth aspect of the present invention is the fuel cell system according to any one of the first to third aspects, wherein the reforming reaction section comprises a plurality of reforming catalysts arranged so that the gases flowing therein are substantially parallel to each other. The reforming catalyst is sequentially connected in series, and the fuel gas and the reforming gas are introduced into the downstream reforming catalyst and the discharge portion where the fuel gas and the reforming gas are discharged from the upstream reforming catalyst. And a duct formed so as to reverse the flow direction of the fuel gas and the reformed gas when the fuel gas and the reformed gas flow from the upstream reforming catalyst to the downstream reforming catalyst, and The volume of the discharge part was made larger than the volume of the supply part.

In a fifth aspect based on the fourth aspect, the volume of the discharge portion is increased from the center of reversal when the flows of the fuel gas and the reformed gas in the duct are reversed toward the outside. .

A sixth invention is the fuel cell system according to any one of the first to fifth inventions, wherein a combustor for generating a heating gas for supplying heat necessary for a reforming reaction and a heating gas are used for the reforming catalyst. A heat exchange unit for supplying heat and a temperature detector arranged at least one on each of the reforming catalysts are provided, and the heating gas of the combustor is controlled so that the temperature of the reforming catalyst falls within a predetermined range. Control the temperature.

[0013]

According to the first aspect of the present invention, the fuel gas introducing section has the first fuel gas inlet section for introducing the fuel gas so as to swirl upstream thereof, and the fuel gas passage in the fuel gas introducing section. It is possible to make the fuel gas uniform by providing the throttle portion that reduces the area and the stirring portion that stirs the fuel gas at the narrowest portion of the throttle portion. Thereby, the temperature distribution in the reforming reaction section can be made uniform, and deterioration of the reforming efficiency and increase of CO due to the reverse shift reaction of the reformed gas can be suppressed.

According to the second aspect of the present invention, the fuel gas is supplied so as to swirl in the direction opposite to the swirling direction of the fuel gas supplied from the first fuel gas inlet section, thereby promoting the stirring in the stirring section. You can

According to the third aspect of the invention, water and hydrocarbon fuel are sufficiently stirred by introducing water from the first fuel gas inlet and hydrocarbon fuel from the second fuel gas inlet, respectively. be able to.

According to the fourth aspect of the invention, by making the volume of the discharge part larger than the volume of the supply part, the fuel gas and the reformed gas can be uniformly introduced into the reforming reaction part on the downstream side,
It is possible to suppress a decrease in reforming efficiency and an increase in CO due to a reverse shift reaction.

According to the fifth aspect of the invention, the volume of the discharge portion is increased from the center of the reversal when the flow of the fuel gas and the reformed gas in the duct is reversed toward the outside, so that the capacity of the downstream side is improved. A more uniform fuel gas and reformed gas can be supplied to the quality reaction section.

According to the sixth aspect of the present invention, at least one temperature detector is provided for each reforming catalyst to control the temperature of the heating gas so that the temperature of the reforming catalyst falls within a predetermined range. It is possible to improve the reforming efficiency and reduce CO more reliably.

[0019]

FIG. 1 shows the configuration of a fuel cell system using the reforming reactor 3 of this embodiment. Here, the fuel cell 5 is a polymer electrolyte fuel cell, and the electrode is equipped with a platinum catalyst for promoting the reaction.

Fuels such as methanol and water for producing the reformed gas are supplied to the evaporator 1 and vaporized by heat exchange with the combustion gas supplied from the combustor 2. The fuel gas composed of vaporized methanol and water, and the combustion gas (hereinafter referred to as heating gas) discharged from the evaporator 1 are supplied to the reforming reactor 3. In the reforming reactor 3, heat exchange is performed between the fuel gas and the heating gas, and the heat is used to reform the fuel gas to generate a hydrogen-rich reformed gas.

Here, if CO is contained in the reformed gas, this CO is adsorbed by the platinum catalyst filled in the fuel cell 5 to lower the function as a catalyst. Therefore, the reaction at the fuel electrode shown in the formula (1) described later is hindered, which causes deterioration of the performance of the fuel cell 5. Therefore, the CO remover 4 is disposed downstream of the reforming reactor 3 to reduce the CO in the reformed gas.
After reducing the concentration, it is supplied to the fuel cell 5. In such a polymer electrolyte fuel cell 5, the permissible value of CO concentration in the supplied gas is usually about several tens of ppm.

The fuel cell 5 for generating power using the reformed gas having a low CO concentration directly converts the chemical energy of the fuel into electrical energy without passing through mechanical energy or thermal energy. As a normal form, a fuel electrode to which a hydrogen-containing gas is supplied and an air electrode to which an oxygen-containing gas is supplied are arranged with an electrolyte layer sandwiched between them. Get power.

[0023]

[Formula 1] Here, the formula (1) represents the reaction at the fuel electrode, the formula (2) represents the reaction at the air electrode, and the formula (3) for the fuel cell 5 as a whole.
The reaction shown in is progressing.

The fuel cell system is constituted by the above components, and the control unit 6 controls each component.

Next, the reforming reactor 3 used in such a fuel cell system will be described.

Steam reforming is one of the fuel reforming means for producing the reformed gas to be supplied to the fuel cell 5 from the fuel gas in the reforming reactor 3. As the fuel gas, hydrocarbon fuels such as methanol, gasoline, and natural gas are used. Here, the steam reforming reaction when methanol is used as the fuel gas will be described.

The reaction when steam reforming methanol is performed by the decomposition reaction of methanol represented by the formula (4) and the reaction represented by the formula (5).
The CO conversion reaction shown in (1) simultaneously proceeds, and is represented by the reaction formula (6) as a whole.

[0028]

[Formula 2] As shown in the equation (6), since the entire steam reforming reaction is an endothermic reaction, it is necessary to supply heat necessary for the reforming reaction to the reforming reactor 3 from the outside. However, when heat is excessively supplied from the outside or when a local high temperature portion is generated in the reforming reactor 3, the reformed gas generated by the equation (6) is used in the high temperature atmosphere. Be exposed to. As a result, the reverse reaction (reverse shift reaction) of the formula (5), which is an endothermic reaction, occurs, and the CO concentration in the reformed gas produced increases. On the other hand, in the case where a low temperature part is locally generated in the reforming reactor 3, the reaction of the formula (6) becomes difficult to proceed, so that the reforming efficiency of methanol decreases.

Therefore, in order to avoid such deterioration of the reforming efficiency and increase of CO due to the reverse shift reaction, in this embodiment, the reforming reactor 3 is constructed as shown in FIG.

The reforming reactor 3 includes a first reforming catalyst 11 and a second reforming catalyst.
Reforming catalyst 13, third reforming catalyst 15 (hereinafter, reforming catalyst 1
1, 13, 15), the first duct part 12, the second
The duct portions 14 (hereinafter, duct portions 12 and 14) are connected in series. The reforming catalysts 11, 13 and 15 are arranged so as to be adjacent to each other via the wall, and the flow of the fuel gas is reversed by the duct portions 12 and 14, so that the supplied fuel gas is supplied to the reforming reactor 3 It meanders inside and flows. Further, each of the duct portions 12 and 14 is composed of a fuel gas discharge portion 12a, 14a from the upstream reforming catalyst and a fuel gas supply portion 12b, 14b to the downstream reforming catalyst.

On the other hand, the heating gas generated in the combustor 2 is introduced into the internal space of the reformer 3 from the heating gas inlet portion 10 and in parallel with the direction in which the reforming catalysts 11, 13 and 15 are arranged, In addition, they flow from the first reforming catalyst 11 toward the third reforming catalyst 15 outside these. At this time, a region where heat is supplied from the heated gas to the reforming catalysts 11, 13, 15 is used as a heat exchange section. The heated gas is discharged from the heated gas outlet portion 18 to the outside. Further, temperature sensors 21, 23, 25 are arranged on the reforming catalysts 11, 13, 15 in order to perform temperature control as will be described later.

The fuel gas vaporized in the evaporator 1 is introduced into the first reforming catalyst 11 from the first fuel gas inlet 7 and the second fuel gas inlet 8 through the fuel gas inlet 9. Here, by arranging the first fuel gas inlet portion 7 at the end and the outermost portion of the fuel gas introducing portion 9, the fuel gas introducing portion 9
A swirl flow of the fuel gas is generated inside. In the present embodiment, the fuel gas introduction part 9 has a cylindrical shape, the first fuel gas inlet part 7 is formed on the cylinder wall surface, and the supplied fuel gas swirls along the cylinder wall surface, that is, in a substantially tangential direction. Arrange to be introduced.

A conical throttle plate 19 for reducing the flow passage area in the direction in which the swirling flow advances toward the first reforming catalyst 11 is arranged in the gas introducing portion 9. Further, a cylindrical stirring section 20 is arranged at the end of the diaphragm plate 19 where the flow passage area is minimized by the diaphragm plate 19. A second fuel gas inlet portion 8 is arranged in the stirring portion 20, and here, the fuel gas supplied is arranged so as to swirl in a direction opposite to the swirling flow of the fuel gas supplied from the first fuel gas inlet portion 7. To do. For example, the flow of the fuel gas introduced from the first fuel gas inlet portion 7 and the second fuel gas inlet portion 8 is arranged in parallel to each other on the opposite outer sides with respect to the center of the fuel gas inlet portion 9. did. For this reason, the fuel gas introduced from the first fuel gas inlet portion 7 and the fuel gas introduced from the second fuel gas inlet portion 8 tend to swirl in opposite directions, so that they cancel each other's flows and stir. As a result, the distribution of the fuel gas can be made uniform and then introduced into the first reforming catalyst 11 arranged downstream of the fuel gas introducing unit 9.

At this time, the first fuel gas inlet portion 7 and the second fuel gas inlet portion 8 may be supplied after generating a mixed gas of water and methanol, but the water and methanol are supplied to the evaporator 1. When vaporized independently, they may be supplied separately and mixed in the reforming reactor 3.
At this time, the flow rate of water is usually 1.5 to
Since it is 2.5 times, water is introduced from the first fuel gas inlet portion 7 on the upstream side where the volume after introduction is large and the second fuel gas on the downstream side where the volume after introduction is small is introduced. It is introduced from the inlet 8. As a result, smooth introduction can be performed, and the stirring unit 20 can sufficiently stir the water and methanol.

The agitated and homogenized fuel gas is supplied to the first reforming catalyst 11, and the reforming reaction is caused by using the heat from the heating gas introduced from the heating gas inlet 10. The unreacted fuel gas that has passed through the first reforming catalyst 11 and the produced reformed gas are guided to the discharge portion 12 a of the first duct portion 12. After that, the flow is reversed (U-turned) along the duct portion 12 and introduced into the second reforming catalyst 13 through the supply portion 12b, and the reforming reaction is performed again.

Here, the volume of the discharge portion 12a of the first duct portion 12 arranged on the outlet side of the first reforming catalyst 11 is the volume of the supply portion 12b arranged on the upstream side of the second reforming catalyst 13. Form larger. Here, since the reforming catalysts 11, 13 and 15 of the present embodiment have plate fins inserted therein, the flow direction of the fuel gas flowing inside is limited to one direction from the inlet to the outlet. Therefore, the flow direction can be smoothly changed by setting the volume of the discharge portion 12a to be large so as to have a sufficient space in which the fuel gas and the reformed gas can freely flow.
Further, the volume of the discharge portion 12a is increased for a while as it goes away from the center of inversion in the cross-sectional direction of the flow of the fuel gas and the reformed gas, that is, toward the outside of the swirl. Here, for example, as shown in FIG. 2, the gas flow path of the first reforming catalyst 11 is changed to the second flow path.
It is configured such that it is long on the reforming catalyst 13 side and gradually shortens as it goes away from the second reforming catalyst 13 side. As described above, as the distance to the second reforming catalyst 13 is longer, the restriction of the flow direction of the reformed gas is eliminated and the free flowing space is enlarged, so that the direction change of the fuel gas and the reformed gas is smoothly performed. It can be carried out. As a result, the uniform fuel gas can be supplied to the second reforming catalyst 13, so that the temperature gradient generated in the second reforming catalyst 13 can be suppressed.

After the reforming reaction has occurred in the second reforming catalyst 13, the mixed gas of the fuel gas and the reforming gas passes through the second duct 14 and is supplied to the third reforming catalyst 15. At this time, similarly to the first duct portion 12 on the outlet side of the first reforming catalyst 11, the volume of the second duct portion 14 on the outlet side of the second reforming catalyst 13 is also opposite to the flowing gas inversion direction. The fuel gas and the reformed gas can be uniformly introduced into the third reforming catalyst 15 by increasing toward the certain first reforming catalyst 11.

The reformed gas generated by the reforming reaction in the third reforming catalyst 15 passes through the reformed gas outlet passage 16 arranged downstream of the third reforming catalyst 15, and the reformed gas outlet section 1
It is discharged from the reforming reactor 3 from 7.

On the other hand, the heating gas supplied from the combustor 2 via the evaporator 1 is supplied from the heating gas inlet 10 to the reforming reactor 3
After being introduced into the interior of the reforming catalyst 11, heat is supplied to the reforming catalysts 11, 13 and 15, and then discharged from the heating gas outlet 18 to the outside of the reforming reactor 3.

FIG. 3 shows the amount of unreacted fuel and the CO concentration in the reformed gas produced when the reforming reaction is carried out using such a reforming reactor 3.

Conventionally, a temperature gradient is generated in the reforming catalysts 11, 13 and 15, so that CO increases due to the reverse shift reaction when the amount of fuel gas is small and unreacted gas increases when the amount of fuel gas increases. The increase, that is, the deterioration of fuel efficiency, is noticeable. On the other hand, when the reforming reactor 3 of the present embodiment is used, the generation of unreacted fuel and CO can be suppressed for the same amount of fuel gas.

Next, a temperature control method for the reforming reactor 3 in the control unit 6 will be described with reference to the flowchart of FIG.

In step S401, the reforming catalyst 1
Temperature sensors 21, 23, 25 arranged at 1, 13, 15
The temperature of the reaction part is determined by a method such as reading the measured values of, and obtaining the average of these measured values. In step S402, it is determined whether the reaction part temperature is equal to or higher than a specified value. If it is equal to or more than the specified value, the process proceeds to step S403, and control such as reducing the flow rate of the combustion fuel supplied to the combustor 2 is performed.
The temperature of the heating gas supplied to the reforming reactor 3 is lowered.
In step S404, it is determined whether the temperature has reached the specified value. If not reached, the process returns to step S403 and the heating gas is further lowered. By repeating this, the temperature of the reaction part is controlled so as to become the specified value.

On the other hand, in step S402, if the reaction part temperature is lower than the specified value, the process proceeds to step S405, and the heating gas temperature is raised by control such as increasing the flow rate of the fuel supplied to the combustor 2. In step S406, it is determined whether the reaction part temperature has reached a specified value,
The steps S405 and 406 are repeated until the temperature reaches the temperature, and the reaction part temperature is controlled so as to reach the specified value.

As in the prior art, the reforming catalysts 11, 13, 15
When a temperature gradient occurs in, it is difficult to consider the temperature at a limited number of points as a representative, which leads to overheating or insufficient heating. However, in the present embodiment, the temperature of the reforming catalysts 11, 13 and 15 becomes substantially uniform by uniformly supplying the fuel gas, so that it is possible to obtain the representative temperature with the minimum temperature measurement. Here, in the present embodiment, the reaction part temperature which is the average temperature of the respective reforming catalysts 11, 13, 15 is adopted, but whether the respective temperatures of the respective reforming catalysts 11, 13, 15 have reached the specified values. You may judge whether. At this time, for example, if the tendency of two or more reforming catalysts is set as the tendency of the reforming reactor 3, and if all three tend to be different, it can be judged from the difference between the specified value and each temperature. The same control as described above can be performed. When the heating gas is independently supplied to each of the reforming catalysts 11, 13, and 15 and the temperature of each heating gas can be controlled, the temperature of each of the reforming catalysts 11, 13, 15 is reacted. Even more accurate control can be achieved by setting the part temperature.

As described above, the fuel gas inlet portion 7 is arranged at the outermost portion of the end portion of the fuel gas introducing portion 9, and the fuel gas introducing portion 9 is provided with the throttle plate 19 and the stirring portion 20 for reducing the flow passage area. Thus, the fuel gas flowing into all the reforming catalysts 11, 13, 15 can be made substantially uniform, and the generation of the temperature gradient in the reforming reaction can be suppressed. At this time, when the flow directions of the fuel gas and the reformed gas are reversed, the flow direction can be smoothly reversed by sufficiently securing a region in which the flow directions can be freely changed. This allows
The fuel gas can be supplied to the downstream reforming catalysts 13 and 15 while maintaining the homogenized state. By supplying the homogenized fuel gas to the reforming catalysts 11, 13, and 15 in this manner, the reforming efficiency is deteriorated due to the temperature decrease, and CO is generated due to the reverse shift reaction caused by the excessive temperature rise.
The increase can be avoided.

Since the fuel gas supply port is the fuel gas inlet 7 provided at the end of the fuel gas inlet 9 and the fuel gas inlet 8 provided at the agitator 20, the agitator 20 agitates the fuel gas. The effect can be promoted.

Further, the reforming catalyst 11 in the fuel gas passage,
By controlling the heating gas temperature according to the temperature at several points in 13 and 15, it is possible to control the heating gas temperature only by measuring the minimum temperature at several points, and also to improve the reforming efficiency and CO
The reduction can be performed more reliably.

Needless to say, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the technical idea described in the claims.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel cell system using a reforming reactor in the present embodiment.

FIG. 2 is a configuration diagram of a reforming reactor according to the present embodiment.

FIG. 3 is a diagram showing the amount of unreacted fuel and CO concentration in the reformed gas generated in the present embodiment.

FIG. 4 is a flowchart showing temperature control of the reforming catalyst according to the present embodiment.

[Explanation of symbols]

2 Combustor 3 reforming reactor 7 First fuel gas inlet 8 Second fuel gas inlet 9 Fuel gas introduction section 11, 13, 15 reforming catalyst 12, 14 Duct part 12a, 14a discharge section 12b, 14b supply unit 19 Diaphragm (diaphragm) 20 Stirrer 21, 23, 25 Temperature sensor (temperature detector)

Claims (6)

[Claims] 1. A reforming reaction section having a reforming catalyst for producing a reformed gas by reforming the fuel gas, and a fuel gas introducing section for introducing the fuel gas to the reforming reaction section, The fuel gas introducing section introduces a fuel gas so as to swirl upstream thereof, a first fuel gas inlet section, a throttle section for reducing a flow passage area of the fuel gas in the fuel gas introducing section, and the throttle section. A stirring unit that stirs the fuel gas in the narrowest part of
A reforming reactor comprising: 2. The second fuel gas inlet part for supplying the fuel gas so as to swirl in a direction opposite to the swirling direction of the fuel gas supplied from the first fuel gas inlet part is arranged in the stirring part. The reforming reactor according to 1. 3. The reforming reactor according to claim 2, wherein water is introduced from the first fuel gas inlet and hydrocarbon-based fuel is introduced from the second fuel gas inlet. 4. The reforming reaction section is composed of a plurality of reforming catalysts arranged so that the gases flowing therein are substantially parallel to each other, and the reforming catalysts are sequentially connected in series to each other. The reforming catalyst comprises a discharge part for discharging the fuel gas and the reformed gas, and a supply part for introducing the fuel gas and the reformed gas to the reforming catalyst on the downstream side. The reforming catalyst on the side is provided with a duct formed so that the flow directions of the fuel gas and the reforming gas are reversed when the reforming gas flows, and the volume of the discharge part is larger than the volume of the supply part. The reforming reactor according to any one of 1 to 3. 5. The reforming reactor according to claim 4, wherein the volume of the discharge section is increased outward from the center of reversal when the flow of the fuel gas and the reformed gas in the duct is reversed. . 6. A combustor for generating heating gas for supplying heat necessary for the reforming reaction, a heat exchange section for supplying heat to the reforming catalyst by using the heating gas, and at least each of the reforming catalyst. The temperature detector arrange | positioned one by one, The temperature of the heating gas of the said combustor is controlled so that the temperature of the said reforming catalyst may be in a predetermined range, The temperature sensor of any one of Claim 1 to 5 characterized by the above-mentioned. Reforming reactor.